Recontouring Military Barrels A Tutorial?

[bert01]

Ive done some searching and dont see much on the site about it. Am I missing something and it sjust so easy nobody post about it. Do you just chuck it up and make chips, or are there some tips and tricks we might need to know?

 

thanks in advance

 

bert

[z1r]

I'd turn it between centers. Rarely will you be able to just cut a straight taper unless you want a really short barrel. Best way to do it is to swamp the barrel.

[bert01]

So between centers, then just follow the first step (smallest diameter) up to a point, then taper out to full chamber diameter. like sporter barrels? Do you have any problem with military barrel warping or bending usually, as long as you are careful when turning?

[z1r]

The only barrel I've had warp on me is an ER Shaw, which is why I won't use another. It was on a super light pass and it still warped. I've done dozens of military barrels and none have walked on me. Keep the heat in the chips, not the barrel. Allow for heat expansion otherwise you will bend (or induce stress into) the barrel.

[Clemson]

If you will study most military barrels, you may be able to come up with a profile that will look better but may not get ALL of every step out. You may, for instance, retain the step where the rear sight sleeve was, but taper the section into the next section. You may be able to cut the muzzle back to eliminate the step at the muzzle where the front sight is. You may be able to taper the section forward of the forend to eliminate that step. Etc, etc. Taking all the steps out results in a pencil thin barrel that is whippy (in my opinion).

 

Clemson

[Ron J]

Z, what's "swamping" the barrel mean? Also, how do you keep the heat in the chip and not the barrel? I've run lathes for some time, (not barrel work), but I've never heard this put this way. Is this a coolant practice?

[z1r]

Z, what's "swamping" the barrel mean? Also, how do you keep the heat in the chip and not the barrel? I've run lathes for some time, (not barrel work), but I've never heard this put this way. Is this a coolant practice?

 

Swamped barrels were used primarily on muzzleloading rifles where the barrel diameter tapers from a large diameter at the breech to a smaller diameter at the mid point then widens again at the muzzle. On Octagon barrels it is used but the mid point is imaginary or well away from the muzzle. Basically you are using two radiuses that intersect. That way you get the quick transition near the receiver then the long slow taper. The way I'm using the term is sort of co-opted. A gunsmith buddy of mine refers to this as swamped and I sort of picked up on it.

 

Most sporter contours have a radius then a straight taper.

 

Another way to convert a milsurp mauser barrel is to use a series of tapers but the trick is blending them. The key is hiding where the differnt straight tapers intersect. Transition is everything.

 

By keeping the heat in the chip I mean keep your tool sharp. The sharper the better. You don't want to try for a smooth finish, you want to remove material witout heating up the barrel. Friction is the enemy. Remember, as the blank heats up it will grow. Loosen up the quill so as to relieve pressure periodically and prevent bending the blank.

 

[Doble Troble]

You don't want to try for a smooth finish

 

I contoured barrels for my 38-55 and 6.5x55 AI between centers on my crudely extended mini-lathe.

 

Because of the crude extention, the saddle wobbled a hair at the intersection of the original bed and the added-on extension. It wasn't much of a wobble, but it made a visual defect in the surface. Because of this I roughed out both of these barrels (the 38-55 was made from a cheap A&B 375 blank, the 6.5 x55 AI from a cheap but excellent 29" Swede surplus bbl) very crudely with fast cuts and finised with files and shoe-shine emery cloth.

 

The rough cuts were made with very sharp tools - because I'm weird about sharpness (ask my wife). Don't test my pocket knife with your thumb or you're liable to lose it. I love hard, sharp steel (almost as much as the chick in the Mercury ads, yes I WILL add it to my list...).

 

OK, I'm distracting myself...

 

The point is that these two contoured barrels have become part of my two most accurate rifles. It might be a coincidence, but Z's post is making me think that by accidently following his turning advice that these turned-out particularly well.